From The Art and Popular Culture Encyclopedia
In linguistics, a homonym is one of a group of words that share the same spelling and the same pronunciation but have different meanings. Some sources only require that homonyms share the same spelling or pronunciation (in addition to having different meanings), but these are the definitions most other sources give for homographs and homophones respectively. The state of being a homonym is called homonymy. Examples of homonyms are stalk (which can mean either part of a plant or to follow someone around), bear (animal) and bear (carry), left (opposite of right) and left (past tense of leave). Some sources also consider the following trio of words to be homonyms, but others designate them as "only" homophones: to, too and two (actually, to, to, too, too and two, being "for the purpose of" as in "to make it easier", the opposite of "from", also, excessively, and "2", respectively). Some sources state that homonym meanings must be unrelated in origin (rather than just different). Thus right (correct) and right (opposed to left) would be polysemous (see below) and not be homonyms.
There is similar confusion about the definition of some of the related terms described below. This article explains what appear to be the "standard" meanings, and variant definitions are then summarised under "Terminological confusion".
The word "homonym" comes from the conjunction of the Greek prefix homo- (meaning same) and suffix -onym (meaning name). Thus, it refers to two or more distinct words sharing the "same name".